Leaded packages play an important role in electronics, but efforts to miniaturize electronic components and assemblies have driven development of technologies that preserve circuit board surface area. Because leaded packages have leads emergent from peripheral sides of the package, leaded packages occupy more than a minimal amount of circuit board surface area. Consequently, alternatives to leaded packages known as chip scale packaging or CSP have recently gained market share.
CSP refers generally to packages that provide connection to an integrated circuit through a set of contacts arrayed across a major surface of the package. Instead of leads emergent from a peripheral side of the package, contacts are placed on a major surface and typically emerge from the planar bottom surface of the package. The absence of “leads” on package sides renders most stacking techniques devised for leaded packages inapplicable for CSP stacking.
The previous known methods for stacking CSPs apparently have various deficiencies including complex structural arrangements and thermal or high frequency performance issues. Thermal performance is a characteristic of importance in CSP stacks. To increase dissipation of heat generated by constituent CSPs, the thermal gradient between the lower CSP and upper CSP in a CSP stack or module should be minimized. Prior art solutions to CSP stacking do not, however, address thermal gradient minimization in disclosed constructions.
As CSP gains in market share, signal complexity and datapath widths reflect the growing trend toward moving ever larger amounts of data at increasing rates and the demand for wider datapath storage increases.
What is needed, therefore, is a technique and system for stacking chipscale packaged integrated circuits in a module that provides a thermally efficient, reliable structure that performs well at higher frequencies and provides datapath flexibility but does not result in a stack of excessive height yet allows production at reasonable cost with readily understood and managed materials and methods.